Consul is an authorization solution for Ruby on Rails where you describe sets of accessible things to control what a user can see or edit.
We have used Consul in combination with assignable_values to solve a variety of authorization requirements ranging from boring to bizarre. Also see our crash course video: Solving bizare authorization requirements with Rails.
Consul is tested with Rails 2.3, 3.2, 4.1, and 4.2.7 on Ruby 1.8.7, 2.1.0, and 2.2.6.
You describe access to your application by putting a Power
model into app/models/power.rb
.
Inside your Power
you can talk about what is accessible for the current user, e.g.
- A scope of records a user may see
- Whether the user is allowed to use a particular screen
- A list of values a user may assign to a particular attribute
A Power
might look like this:
class Power
include Consul::Power
def initialize(user)
@user = user
end
power :users do
User if @user.admin?
end
power :notes do
Note.by_author(@user)
end
power :dashboard do
true # not a scope, but a boolean power. This is useful to control access to stuff that doesn't live in the database.
end
end
There are no restrictions on the name or constructor arguments of your this class.
You can deposit all kinds of objects in your power. See the sections below for details.
A typical use case in a Rails application is to restrict access to your ActiveRecord models. For example:
- Anonymous visitors may only see public posts
- Users may only see their own notes
- Only admins may edit users
You do this by making your powers return an ActiveRecord scope (or "relation"):
class Power
...
power :notes do
Note.by_author(@user)
end
power :users do
User if @user.admin?
end
end
You can now query these powers in order to retrieve the scope:
power = Power.new(user)
power.notes # => returns an ActiveRecord::Scope
Or you can ask if the power is given (meaning it's not nil
):
power.notes? # => returns true if Power#notes returns a scope and not nil
Or you can raise an error unless a power its given, e.g. to guard access into a controller action:
power.notes! # => raises Consul::Powerless unless Power#notes returns a scope (even if it's empty)
Or you ask whether a given record is included in its scope (can be optimized):
power.note?(Note.last) # => returns whether the given Note is in the Power#notes scope. Caches the result for subsequent queries.
Or you can raise an error unless a given record is included in its scope:
power.note!(Note.last) # => raises Consul::Powerless unless the given Note is in the Power#notes scope
See our crash course video Solving bizare authorization requirements with Rails for many different use cases you can cover with this pattern.
If you have different access rights for e.g. viewing or updating posts, simply use different powers:
class Power
...
power :notes do
Note.published
end
power :updatable_notes do
Note.by_author(@user)
end
power :destroyable_notes do
Note if @user.admin?
end
end
There is also a shortcut to map different powers to RESTful controller actions.
Boolean powers are useful to control access to stuff that doesn't live in the database:
class Power
...
power :dashboard do
true
end
end
You can query it like the other powers:
power = Power.new(@user)
power.dashboard? # => true
power.dashboard! # => raises Consul::Powerless unless Power#dashboard? returns true
Note that there is a difference between having access to an empty list of records, and having no access at all.
If you want to express that a user has no access at all, make the respective power return nil
.
Note how the power in the example below returns nil
unless the user is an admin:
class Power
...
power :users do
User if @user.admin?
end
end
When a non-admin queries the :users
power, she will get the following behavior:
power = Power.new(@user)
power.users # => returns nil
power.users? # => returns false
power.users! # => raises Consul::Powerless
power.user?(User.last) # => returns false
power.user!(User.last) # => raises Consul::Powerless
Sometimes it is not convenient to define powers as a collection or scope (relation). Sometimes you only want to store a method that checks whether a given object is accessible.
To do so, simply define a power that ends in a question mark:
class Power
...
power :updatable_post? do |post|
post.author == @user
end
end
You can query such an power as always:
power = Power.new(@user)
power.updatable_post?(Post.last) # return true if the author of the post is @user
power.updatable_post!(Post.last) # raises Consul::Powerless unless the author of the post is @user
A power can return any type of object. For instance, you often want to return an array:
class Power
...
power :assignable_note_states do
if admin?
%w[draft pending published retracted]
else
%w[draft pending]
end
end
end
You can query it like any other power. E.g. if a non-admin queries this power she will get the following behavior:
power.assignable_note_states # => ['draft', 'pending']
power.assignable_note_states? # => returns true
power.assignable_note_states! # => does nothing (because the power isn't nil)
power.assignable_note_state?('draft') # => returns true
power.assignable_note_state?('published') # => returns false
power.assignable_note_state!('published') # => raises Consul::Powerless
You can define multiple powers at once by giving multiple power names:
class Power
...
power :destroyable_users, :updatable_users do
User if admin?
end
end
Sometimes it can be useful to define powers that require context. To do so, just take an argument in your power
block:
class Power
...
power :client_notes do |client|
client.notes.where(:state => 'published')
end
end
When querying such a power, you always need to provide the context, e.g.:
client = ...
note = ...
Power.current.client_note?(client, note)
You can query a scope power for a given record, e.g.
class Power
...
power :posts do |post|
Post.where(:author_id => @user.id)
end
end
power = Power.new(@user)
power.post?(Post.last)
What Consul does internally is fetch all the IDs of the power.posts
scope and test if the given
record's ID is among them. This list of IDs is cached for subsequent calls, so you will only touch the database once.
As scary as it might sound, fetching all IDs of a scope scales quiet nicely for many thousand records. There will however be the point where you want to optimize this.
What you can do in Consul is to define a second power that checks a given record in plain Ruby:
class Power
...
power :posts do |post|
Post.where(:author_id => @user.id)
end
power :post? do |post|
post.author_id == @user.id
end
end
This way you do not need to touch the database at all.
Consul has no built-in support for role-based permissions, but you can easily implement it yourself. Let's say your User
model has a string column role
which can be "author"
or "admin"
:
class Power
include Consul::Power
def initialize(user)
@user = user
end
power :notes do
case role
when :admin then Note
when :author then Note.by_author
end
end
private
def role
@user.role.to_sym
end
end
It is convenient to expose the power for the current request to the rest of the application. Consul will help you with that if you tell it how to instantiate a power for the current request:
class ApplicationController < ActionController::Base
include Consul::Controller
current_power do
Power.new(current_user)
end
end
You now have a helper method current_power
for your controller and views. Everywhere else, you can access it from Power.current
. The power will be instantiated when the request is handed over from routing to ApplicationController
, and will be nilified once the request was processed.
You can now use power scopes to control access:
class NotesController < ApplicationController
def show
@note = current_power.notes.find(params[:id])
end
end
To make sure a power is given before every action in a controller:
class NotesController < ApplicationController
power :notes
end
You can use :except
and :only
options like in before_actions.
You can also map different powers to different actions:
class NotesController < ApplicationController
power :notes, :map => { [:edit, :update, :destroy] => :changeable_notes }
end
Actions that are not listed in :map
will get the default action :notes
.
Note that in moderately complex authorization scenarios you will often find yourself writing a map like this:
class NotesController < ApplicationController
power :notes, :map => {
[:edit, :update] => :updatable_notes,
[:new, :create] => :creatable_notes,
[:destroy] => :destroyable_notes
}
end
Because this pattern is so common, there is a shortcut :crud
to do the same:
class NotesController < ApplicationController
power :crud => :notes
end
And if your power requires context (is parametrized), you can give it using the :context
method:
class ClientNotesController < ApplicationController
power :client_notes, :context => :load_client
private
def load_client
@client ||= Client.find(params[:client_id])
end
end
It is often convenient to map a power scope to a private controller method:
class NotesController < ApplicationController
power :notes, :as => :note_scope
def show
@note = note_scope.find(params[:id])
end
end
This is especially useful when you are using a RESTful controller library like resource_controller. The mapped method is aware of the :map
option.
When using nested resources you probably want two power checks and method mappings: One for the parent resource, another for the child resource.
Say you have the following routes:
resources :clients do
resources :notes
end
And the following power definitions:
class Power
...
power :clients do |client|
Client.active if signed_in?
end
power :client_notes do |client|
client.notes.where(:state => 'published')
end
end
You can now check and map both powers in the nested NotesController
:
class NotesController < ApplicationController
power :clients, :as => :client_scope
power :client_notes, :context => :load_client, :as => :note_scope
def show
load_note
end
private
def load_client
@client ||= client_scope.find(params[:client_id])
end
def load_note
@note ||= note_scope.find(params[:id])
end
end
Note how we provide the Client
parameter for the :client_notes
power by using the :context => :load_client
option in the power
directive.
You can force yourself to use a power
check in every controller. This will raise Consul::UncheckedPower
if you ever forget it:
class ApplicationController < ActionController::Base
include Consul::Controller
require_power_check
end
Should you for some obscure reason want to forego the power check:
class ApiController < ApplicationController
skip_power_check
end
Sometimes a scope is not enough to express what a user can edit. You will often want to give a user write access to a record, but restrict the values she can assign to a given field.
Consul leverages the assignable_values gem to add an optional authorization layer to your models. This layer adds additional validations in the context of a request, but skips those validations in other contexts (console, background jobs, etc.).
You can enable the authorization layer by using the macro authorize_values_for
:
class Story < ActiveRecord::Base
authorize_values_for :state
end
The macro defines an accessor power
on instances of Story
. If that field is set to a power, the values of state
will be validated against a whitelist of values provided by that power. If that field is nil
, the validation is skipped.
Here is a power implementation that can provide a list of assignable values for the example above:
class Power
...
def assignable_story_states(story)
if admin?
['delivered', 'accepted', 'rejected']
else
['delivered']
end
end
end
Here you can see how to activate the authorization layer and use the new validations:
story = Story.new
Power.current = Power.new(:role => :guest) # activate the authorization layer
story.assignable_states # ['delivered'] # apparently we're not admins
story.state = 'accepted' # a disallowed value
story.valid? # => false
story.state = 'delivered' # an allowed value
story.valid? # => true
You can not only authorize scalar attributes like strings or integers that way, you can also authorize belongs_to
associations:
class Story < ActiveRecord::Base
belongs_to :project
authorize_values_for :project
end
class Power
...
power :assignable_story_projects do |story|
user.account.projects
end
end
The authorize_values_for
macro comes with many useful options and details best explained in the assignable_values README, so head over there for more. The macro is basically a shortcut for this:
assignable_values_for :field, :through => lambda { Power.current }
Consul gives you a way to dynamically access and query powers for a given name, model class or record. A common use case for this are generic helper methods, e.g. a method to display an "edit" link for any given record if the user is authorized to change that record:
module CrudHelper
def edit_record_action(record)
if current_power.include_record?(:updatable, record)
link_to 'Edit', [:edit, record]
end
end
end
You can find a full list of available dynamic calls below:
Dynamic call | Equivalent |
---|---|
Power.current.send(:notes) |
Power.current.notes |
Power.current.include_power?(:notes) |
Power.current.notes? |
Power.current.include_power!(:notes) |
Power.current.notes! |
Power.current.include_object?(:notes, Note.last) |
Power.current.note?(Note.last) |
Power.current.include_object!(:notes, Note.last) |
Power.current.note!(Note.last) |
Power.current.for_record(Note.last) |
Power.current.notes |
Power.current.for_record(:updatable, Note.last) |
Power.current.updatable_notes |
Power.current.for_model(Note) |
Power.current.notes |
Power.current.for_model(:updatable, Note) |
Power.current.updatable_notes |
Power.current.include_model?(Note) |
Power.current.notes? |
Power.current.include_model?(:updatable, Note) |
Power.current.updatable_notes? |
Power.current.include_model!(Note) |
Power.current.notes! |
Power.current.include_model!(:updatable, Note) |
Power.current.updatable_notes! |
Power.current.include_record?(Note.last) |
Power.current.note?(Note.last) |
Power.current.include_record?(:updatable, Note.last) |
Power.current.updatable_note?(Note.last) |
Power.current.include_record!(Note.last) |
Power.current.note!(Note.last) |
Power.current.include_record!(:updatable, Note.last) |
Power.current.updatable_note!(Note.last) |
Power.current.name_for_model(Note) |
:notes |
Power.current.name_for_model(:updatable, Note) |
:updatable_notes |
Power.current.name_for_record(Note.last) |
:notes |
Power.current.name_for_record(:updatable, Note.last) |
:updatable_notes |
You will often want to access Power.current
from another model, to e.g. iterate through the list of accessible users:
class UserReport
def data
Power.current.users.collect do |user|
[user.name, user.email, user.income]
end
end
end
Good practice is for your model to not crash when Power.current
is nil
. This is the case when your model isn't
called as part of processing a browser request, e.g. on the console, during tests and during batch processes.
In such cases your model should simply skip authorization and assume that all users are accessible:
class UserReport
def data
accessible_users = Power.current.present? ? Power.current.users : User
accessible_users.collect do |user|
[user.name, user.email, user.income]
end
end
end
Because this pattern is so common, the Power
class comes with a number of class methods you can use to either query
Power.current
or, if it is not set, just assume that everything is accessible:
class UserReport
def data
Power.for_model(User).collect do |user|
[user.name, user.email, user.income]
end
end
end
There is a long selection of class methods that behave neutrally in case Power.current
is nil
:
Call | Equivalent |
---|---|
Power.for_model(Note) |
Power.current.present? ? Power.current.notes : Note |
Power.for_model(:updatable, Note) |
Power.current.present? ? Power.current.updatable_notes : Note |
Power.include_model?(Note) |
Power.current.present? ? Power.notes? : true |
Power.include_model?(:updatable, Note) |
Power.current.present? ? Power.updatable_notes? : true |
Power.include_model!(Note) |
Power.notes! if Power.current.present? |
Power.include_model!(:updatable, Note) |
Power.updatable_notes! if Power.current.present? |
Power.for_record(Note.last) |
Power.current.present? ? Power.current.notes : Note |
Power.for_record(:updatable, Note.last) |
Power.current.present? ? Power.current.updatable_notes : Note |
Power.include_record?(Note.last) |
Power.current.present? ? Power.note?(Note.last) : true |
Power.include_record?(:updatable, Note.last) |
Power.current.present? ? Power.updatable_note?(Note.last?) : true |
Power.include_record!(Note.last) |
Power.note!(Note.last) if Power.current.present? |
Power.include_record!(:updatable, Note.last) |
Power.updatable_note!(Note.last) if Power.current.present? |
This section Some hints for testing authorization with Consul.
You can say this in any controller spec:
describe CakesController do
it { should check_power(:cakes) }
end
You can test against all options of the power
macro:
describe CakesController do
it { should check_power(:cakes, :map => { [:edit, :update] => :updatable_cakes }) }
end
When you set Power.current
to a power in an RSpec example, you must remember to nilify it afterwards. Otherwise other examples will see your global changes.
A better way is to use the .with_power
method to change the current power for the duration of a block:
admin = User.new(:role => 'admin')
admin_power = Power.new(admin)
Power.with_power(admin_power) do
# run code that uses Power.current
end
Power.current
will be nil
(or its former value) after the block has ended.
A nice shortcut is that when you call with_power
with an argument that is not already a Power
, Consul will instantiate a Power
for you:
admin = User.new(:role => 'admin')
Power.with_power(admin) do
# run code that uses Power.current
end
There is also a method .without_power
that runs a block without a current Power:
Power.without_power do
# run code that should not see a Power
end
Add the following to your Gemfile
:
gem 'consul'
Now run bundle install
to lock the gem into your project.
Test applications for various Rails versions lives in spec
. You can run specs from the project root by saying:
rake all:bundle
rake all:spec
If you would like to contribute:
- Fork the repository.
- Push your changes with specs.
- Send me a pull request.
I'm very eager to keep this gem leightweight and on topic. If you're unsure whether a change would make it into the gem, talk to me beforehand.
Henning Koch from makandra